The paper presents a method for calculating the back electromotive force and cogging torque waveforms of surface permanent-magnet motors using a model based on conformal mapping and magnetic equivalent circuits. The model takes into account the saturation of the iron core and its variation due to rotor movement. Because of the shorter execution time and achieved accuracy, it represents a good alternative to time-consuming finite-element-based models, especially in an initial stage of motor design. The proposed method has been implemented and evaluated on selected examples of 36-slot / 6-pole motors with different levels of saturation in teeth and stator yoke, and shows excellent agreement with the results obtained using finite-element method.